As technology development and demand for mobile devices have increased, demand for secondary batteries as an energy source has rapidly increased. Conventionally, nickel-cadmium batteries or hydrogen ion batteries have been used as secondary batteries. However, lithium secondary batteries have recently widely used which are free from charging and discharging due to little memory effect compared with nickel-based secondary batteries, have a low self-discharge rate and a high energy density.
Such a lithium secondary battery mainly uses a lithium oxide and a carbonaceous material as a positive electrode active material and a negative electrode active material, respectively. The lithium secondary battery includes an electrode assembly in which a positive electrode plate and a negative electrode plate, respectively coated with such a positive electrode active material and a negative electrode active material, are arranged with a separator therebetween, and an outer material, that is, a battery case, for sealing and storing the electrode assembly together with an electrolyte solution.
The lithium secondary battery includes a positive electrode, a negative electrode, the separator therebetween, and an electrolyte. Depending on which one of the positive electrode active material and the negative electrode active material is used, the lithium secondary battery may be divided into a lithium ion battery (LIB), a polymer lithium ion battery (PLIB), and so on. Generally, electrodes of these lithium secondary batteries are formed by applying the positive electrode active material or the negative electrode active material to a current collector of aluminum or copper in a shape such as a sheet, a mesh, a film, and a foil, and by drying thereafter.
Generally, the battery module of the secondary battery may be combined with a casing to protect internal components from vibration or shock. However, when welding is used to fix the casing, thermal damage may occur in a battery cell inside the casing due to heat generated from the welding, and even if damage occurs by other various causes in the battery cell inside the casing, it may not be easy to remove the casing combined with the battery cell, so that it is difficult to replace or repair a damaged battery cell.